Which city has the germiest cabs, buses and trains?

Whether it's hopping on a city bus or hailing a taxi, public transportation has the reputation of being a bacteria hotbed. But are all cities equally grimy?

Jeff Rossen and the Rossen Reports team used a bacteria meter to test public transportation systems across New York City, Los Angeles and Chicago to see how dirty they really are. Health experts say anything over 100 is a fail.

Are buses cleaner than subways? What about taxis? Let's check out the results.

NBC Medical contributor Dr. John Torres warned that exposure to this bacteria isn't as harmless as we might assume.

"It's simple how fast it can happen. You touch the pole, you wipe your nose, you wipe your eye, you don't even think about it, bam, you're sick."